Zinc Porphyrin

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Francis Dsouza - One of the best experts on this subject based on the ideXlab platform.

  • a two point bound Zinc Porphyrin Zinc phthalocyanine fullerene supramolecular triad for sequential energy and electron transfer
    Chemical Communications, 2013
    Co-Authors: Kei Ohkubo, Shunichi Fukuzumi, Paul A Karr, Francis Dsouza
    Abstract:

    A novel supramolecular triad composed of a Zinc Porphyrin–Zinc phthalocyanine dyad and fullerenes has been assembled using a ‘two-point’ axial binding approach, and occurrence of efficient photoinduced energy transfer followed by electron transfer is demonstrated.

  • sequential photoinduced energy and electron transfer directed improved performance of the supramolecular solar cell of a Zinc Porphyrin Zinc phthalocyanine conjugate modified tio2 surface
    Journal of Physical Chemistry C, 2013
    Co-Authors: Kati Stranius, Navaneetha K Subbaiyan, Preston Dsouza, Helge Lemmetyinen, Nikolai V Tkachenko, Francis Dsouza
    Abstract:

    Improved performance of a photosynthetic antenna–reaction center mimicking supramolecular solar cell is demonstrated. Toward this, Porphyrin–phthalocyanine conjugates connected by amide linkers, as wide-band capturing solar energy harvesting materials, have been newly synthesized and characterized. Efficient singlet–singlet energy transfer from the Zinc or free-base Porphyrin to phthalocyanine is evidenced from steady-state emission and transient absorption studies in nonpolar and polar solvents. Further, the dyad was immobilized via axial coordination of Zinc Porphyrin of the dyad on semiconducting TiO2 surface modified with axial coordinating ligand functionality, phenylimidazole. Photoelectrochemical studies revealed improved performance of this cell compared to either Zinc Porphyrin or Zinc phthalocyanine only modified electrodes under similar experimental conditions. Transient absorption studies performed on the dyad immobilized on glass/TiO2 surface suggested that upon excitation of the axially coor...

  • enhanced photocurrents via redox modulation by fluoride binding to oxoPorphyrinogen in a Zinc Porphyrin oxoPorphyrinogen surface modified tio2 supramolecular solar cell
    Chemical Communications, 2011
    Co-Authors: Navaneetha K Subbaiyan, Shunichi Fukuzumi, Jonathan P Hill, Katsuhiko Ariga, Francis Dsouza
    Abstract:

    A novel approach for improving photocurrent in a supramolecular solar cell, composed of Zinc Porphyrin-oxoPorphyrinogen (ZnP-OxP) surface-modified TiO2, by redox tuning through fluoride anion binding to the redox active host, OxP is demonstrated.

  • ultrafast excitation transfer and charge stabilization in a newly assembled photosynthetic antenna reaction center mimic composed of boron dipyrrin Zinc Porphyrin and fullerene
    Faraday Discussions, 2011
    Co-Authors: Francis Dsouza, Mohamed E Elkhouly, Helge Lemmetyinen, Nikolai V Tkachenko, Melvin E Zandler, Channa A Wijesinghe, Jessica Hudson, Marja Niemi, Shunichi Fukuzumi
    Abstract:

    A self-assembled supramolecular triad as a model to mimic the light-induced events of the photosynthetic antenna-reaction center, that is, ultrafast excitation transfer followed by electron transfer ultimately generating a long-lived charge-separated state, has been accomplished. Boron dipyrrin (BDP), Zinc Porphyrin (ZnP) and fullerene (C60), respectively, constitute the energy donor, electron donor and electron acceptor segments of the antenna-reaction center imitation. Unlike in the previous models, the BDP entity was placed between the electron donor, ZnP and electron acceptor, C60 entities. For the construction, benzo-18-crown-6 functionalized BDP was synthesized and subsequently reacted with 3,4-dihydroxyphenyl functionalized ZnP through the central boron atom to form the crown-BDP-ZnP dyad. Next, an alkyl ammonium functionalized fullerene was used to self-assemble the crown ether entity of the dyad via ion–dipole interactions. The newly formed supramolecular triad was fully characterized by spectroscopic, computational and electrochemical methods. Steady-state fluorescence and excitation studies revealed the occurrence of energy transfer upon selective excitation of the BDP in the dyad. Further studies involving the pump–probe technique revealed excitation transfer from the 1BDP* to ZnP to occur in about 7 ps, much faster than that reported for other systems in this series of triads, as a consequence of shorter distance between the entities. Upon forming the supramolecular triad by self-assembling fullerene, the 1ZnP* produced by direct excitation or by energy transfer mechanism resulted in an initial electron transfer to the BDP entity. The charge recombination resulted in the population of the triplet excited state of C60, from where additional electron transfer occurred to produce C60•−:crown-BDP-ZnP•+ ion pair as the final charge-separated species. Nanosecond transient absorption studies revealed the lifetime of the charge-separated state to be ∼100 μs, the longest ever reported for this type of antenna-reaction center mimics, indicating better charge stabilization as a result of the different disposition of the entities of the supramolecular triad.

  • photosynthetic antenna reaction center mimicry sequential energy and electron transfer in a self assembled supramolecular triad composed of boron dipyrrin Zinc Porphyrin and fullerene
    Journal of Physical Chemistry A, 2009
    Co-Authors: Eranda Maligaspe, Navaneetha K Subbaiyan, Helge Lemmetyinen, Nikolai V Tkachenko, Melvin E Zandler, Raghu Chitta, Francis Dsouza
    Abstract:

    A self-assembled supramolecular triad, a model to mimic the photochemical events of photosynthetic antenna−reaction center, viz., sequential energy and electron transfer, has been newly constructed and studied. Boron dipyrrin, Zinc Porphyrin, and fullerene respectively constitute the energy donor, electron donor, and electron acceptor segments of the antenna−reaction center mimicry. For the construction, first, boron dipyrrin was covalently attached to a Zinc Porphyrin entity bearing a benzo-18-crown-6 host segment at the opposite end of the Porphyrin ring. Next, an alkyl ammonium functionalized fullerene was used to self-assemble the crown ether entity via ion−dipole interactions. The newly formed supramolecular triad was fully characterized by spectroscopic, computational, and electrochemical methods. Selective excitation of the boron dipyrrin moiety in the dyad resulted in energy transfer over 97% efficiency creating singlet excited Zinc Porphyrin. The rate of energy transfer from the decay measurement...

Shunichi Fukuzumi - One of the best experts on this subject based on the ideXlab platform.

  • a simple Zinc Porphyrin ndi dyad system generates a light energy to proton potential across a lipid membrane
    Dyes and Pigments, 2015
    Co-Authors: Melissa M A Kelson, Shunichi Fukuzumi, Kei Ohkubo, Rajesh S Bhosale, Lathe A Jones, Sidhanath V Bhosale, Akhil Gupta
    Abstract:

    We report a simple donor-acceptor dyad system capable of acting as an artificial mimic of the photosynthetic apparatus by transporting electrons across a lipid bilayer resulting in the conversion of light energy to a proton potential. The active dyad described here consists of a Zinc-Porphyrin as a donor and NDI as an acceptor, connected through a dithiophene spacer. Incorporation of the dyad into a lipid bilayer, followed by excitation of the Zinc-Porphyrin, resulted in charge separation to create a reduction potential near the inner surface and an oxidation potential near the outer surface. This led to transmembrane electron transfer where quinone was converted into hydroquinone inside the vesicle by accepting protons from the HPTS dye, creating a pH gradient. This phenomenon was supported by use of a control molecule without an appropriate spacer and electrochemical and photophysical measurements further support the existence of charge separated states and formation of stable radicals.

  • a two point bound Zinc Porphyrin Zinc phthalocyanine fullerene supramolecular triad for sequential energy and electron transfer
    Chemical Communications, 2013
    Co-Authors: Kei Ohkubo, Shunichi Fukuzumi, Paul A Karr, Francis Dsouza
    Abstract:

    A novel supramolecular triad composed of a Zinc Porphyrin–Zinc phthalocyanine dyad and fullerenes has been assembled using a ‘two-point’ axial binding approach, and occurrence of efficient photoinduced energy transfer followed by electron transfer is demonstrated.

  • enhanced photocurrents via redox modulation by fluoride binding to oxoPorphyrinogen in a Zinc Porphyrin oxoPorphyrinogen surface modified tio2 supramolecular solar cell
    Chemical Communications, 2011
    Co-Authors: Navaneetha K Subbaiyan, Shunichi Fukuzumi, Jonathan P Hill, Katsuhiko Ariga, Francis Dsouza
    Abstract:

    A novel approach for improving photocurrent in a supramolecular solar cell, composed of Zinc Porphyrin-oxoPorphyrinogen (ZnP-OxP) surface-modified TiO2, by redox tuning through fluoride anion binding to the redox active host, OxP is demonstrated.

  • ultrafast excitation transfer and charge stabilization in a newly assembled photosynthetic antenna reaction center mimic composed of boron dipyrrin Zinc Porphyrin and fullerene
    Faraday Discussions, 2011
    Co-Authors: Francis Dsouza, Mohamed E Elkhouly, Helge Lemmetyinen, Nikolai V Tkachenko, Melvin E Zandler, Channa A Wijesinghe, Jessica Hudson, Marja Niemi, Shunichi Fukuzumi
    Abstract:

    A self-assembled supramolecular triad as a model to mimic the light-induced events of the photosynthetic antenna-reaction center, that is, ultrafast excitation transfer followed by electron transfer ultimately generating a long-lived charge-separated state, has been accomplished. Boron dipyrrin (BDP), Zinc Porphyrin (ZnP) and fullerene (C60), respectively, constitute the energy donor, electron donor and electron acceptor segments of the antenna-reaction center imitation. Unlike in the previous models, the BDP entity was placed between the electron donor, ZnP and electron acceptor, C60 entities. For the construction, benzo-18-crown-6 functionalized BDP was synthesized and subsequently reacted with 3,4-dihydroxyphenyl functionalized ZnP through the central boron atom to form the crown-BDP-ZnP dyad. Next, an alkyl ammonium functionalized fullerene was used to self-assemble the crown ether entity of the dyad via ion–dipole interactions. The newly formed supramolecular triad was fully characterized by spectroscopic, computational and electrochemical methods. Steady-state fluorescence and excitation studies revealed the occurrence of energy transfer upon selective excitation of the BDP in the dyad. Further studies involving the pump–probe technique revealed excitation transfer from the 1BDP* to ZnP to occur in about 7 ps, much faster than that reported for other systems in this series of triads, as a consequence of shorter distance between the entities. Upon forming the supramolecular triad by self-assembling fullerene, the 1ZnP* produced by direct excitation or by energy transfer mechanism resulted in an initial electron transfer to the BDP entity. The charge recombination resulted in the population of the triplet excited state of C60, from where additional electron transfer occurred to produce C60•−:crown-BDP-ZnP•+ ion pair as the final charge-separated species. Nanosecond transient absorption studies revealed the lifetime of the charge-separated state to be ∼100 μs, the longest ever reported for this type of antenna-reaction center mimics, indicating better charge stabilization as a result of the different disposition of the entities of the supramolecular triad.

  • fast self exchange electron transfer and delocalization of unpaired electron between Zinc Porphyrin radical cations and Zinc Porphyrins
    Journal of Porphyrins and Phthalocyanines, 2003
    Co-Authors: Shunichi Fukuzumi, Taku Hasobe, Kei Ohkubo, Yoshito Endo, Hiroshi Imahori
    Abstract:

    Self-exchange electron transfer rates between π-radical cations of Zinc Porphyrins and the neutral metalloPorphyrins have been determined from the line-width broadening in the ESR spectra in different solvents at various temperatures. Fine tuning of the substituent on the Porphyrin ring and the proper choice of the solvent have enabled us to observe negative activation enthalpies for the self-exchange electron transfer reactions. The observation of negative activation enthalpies indicates that the self-exchange electron transfer occurs via the charge-transfer π-complexes formed between Zinc Porphyrin radical cations and the neutral Zinc Porphyrins. The complete delocalization of the unpaired electron over two Porphyrin moieties is observed in the radical cation of a Zinc Porphyrin dimer, 5,5'-bis(10,20-bis(3,5-di-tert-butylphenyl)PorphyrinatoZinc(II)). This is regarded as the extreme limit of the rapid self-exchange electron transfer between Zinc Porphyrin radical cation and the neutral form.

Osamu Ito - One of the best experts on this subject based on the ideXlab platform.

  • control of photoinduced energy and electron transfer steps in Zinc Porphyrin oligothiophene fullerene linked triads with solvent polarity
    Journal of Physical Chemistry B, 2005
    Co-Authors: Takumi Nakamura, Mamoru Fujitsuka, Osamu Ito, Junya Ikemoto, Yasuyuki Araki, Kazuo Takimiya, Yoshio Aso, Tetsuo Otsubo
    Abstract:

    The dramatic changes of the lifetimes of the charge-separated (CS) states were confirmed in Zinc Porphyrin (ZnP)−oligothiophene (nT)−fullerene (C60) linked triads (ZnP−nT−C60) with the solvent polarity. After the selective excitation of the ZnP moiety of ZnP−nT−C60, an energy transfer took place from the 1ZnP* moiety to the C60 moiety, generating ZnP−nT−1C60*. In polar solvents, the CS process also took place directly via the 1ZnP* moiety, generating ZnP•+−nT−C60•-, as well as the energy transfer to the C60 moiety. After this energy transfer, an indirect CS process took place from the 1C60* moiety. In the less polar solvent anisole, the radical cation (hole) of ZnP•+−nT−C60•- shifted to the nT moiety; thus, the nT moiety behaves as a cation trapper, and the rates of the hole shift were evaluated to be in the order of 108 s-1; then, the final CS states ZnP−nT•+−C60•- were lasting for 6−7 μs. In the medium polar solvent o-dichlorobenzene (o-DCB), ZnP−nT•+−C60•- and ZnP•+−nT−C60•- were present as an equilibr...

  • photoinduced electron and energy transfer processes of 60 fullerene covalently bonded with one and two Zinc Porphyrin s effects of coordination of pyridine and diazabicyclooctane to zn atom
    Journal of Materials Chemistry, 2005
    Co-Authors: Atula S D Sandanayaka, Yasuyuki Araki, Keiichiro Ikeshita, Nobuhiro Kihara, Yoshio Furusho, Toshikazu Takata, Osamu Ito
    Abstract:

    C60–Zinc Porphyrin (ZnP) dyad (ZnP–C60) and triad (ZnP–C60–ZnP) were synthesized to probe energy-transfer and electron-transfer processes in the absence and presence of pyridine and diazabicyclooctane (DABCO). The syntheses of C60–ZnP and ZnP–C60–ZnP were carried out by Diels–Alder cycloaddition between sulfolene moiety-containing Porphyrin and C60. The photoinduced electron-transfer processes between the spatially positioned C60 and ZnP in the dyad and triad systems were investigated by time-resolved transient absorption and fluorescence measurements with changing solvent polarity. Upon excitation of the ZnP moiety, charge separation via an excited singlet state of ZnP takes place competitively with energy transfer to C60 generating the excited singlet state of C60, from which charge-separated states (ZnP˙+–C60˙− and ZnP˙+–C60˙−–ZnP) are also generated in polar solvents. Rates and efficiencies of energy transfer and charge separation for the triad are higher than those of the dyad. The generated charge-separated species recombine with lifetimes in the rage of 240–330 ns in polar solvents such as DMF, PhCN, and THF for both dyad and triad. In o-dichlorobenzene, although the lifetimes of charge-separated states are very short (<20 ns), coordination of DABCO and pyridine to ZnP in the dyad and triad producing relatively stable coordinated complexes gives rise to prolongation of the charge-separated states up to 460 ns.

  • energy transfer followed by electron transfer in a supramolecular triad composed of boron dipyrrin Zinc Porphyrin and fullerene a model for the photosynthetic antenna reaction center complex
    Journal of the American Chemical Society, 2004
    Co-Authors: Francis Dsouza, Yasuyuki Araki, Melvin E Zandler, Phillip M Smith, Amy L Mccarty, Mitsunari Itou, Osamu Ito
    Abstract:

    The first example of a working model of the photosynthetic antenna-reaction center complex, constructed via self-assembled supramolecular methodology, is reported. For this, a supramolecular triad is assembled by axially coordinating imidazole-appended fulleropyrrolidine to the Zinc center of a covalently linked Zinc Porphyrin−boron dipyrrin dyad. Selective excitation of the boron dipyrrin moiety in the boron dipyrrin−Zinc Porphyrin dyad resulted in efficient energy transfer (kENTsinglet = 9.2 × 109 s-1; ΦENTsinglet = 0.83) creating singlet excited Zinc Porphyrin. Upon forming the supramolecular triad, the excited Zinc Porphyrin resulted in efficient electron transfer to the coordinated fullerenes, resulting in a charge-separated state (kcssinglet = 4.7 × 109 s-1; ΦCSsinglet = 0.9). The observed energy transfer followed by electron transfer in the present supramolecular triad mimics the events of natural photosynthesis. Here, the boron dipyrrin acts as antenna chlorophyll that absorbs light energy and tra...

  • photochemical and electrochemical properties of Zinc chlorin c60 dyad as compared to corresponding free base chlorin c60 free base Porphyrin c60 and Zinc Porphyrin c60 dyads
    Journal of the American Chemical Society, 2001
    Co-Authors: Hiroshi Imahori, Mamoru Fujitsuka, Jianguo Shao, Yihui Chen, Ravindra Pandey, Osamu Ito
    Abstract:

    The photochemical and electrochemical properties of four chlorin−C60 or Porphyrin−C60 dyads having the same short spacer between the macrocycle and the fullerene are examined. In contrast with all the previous results on Porphyrin−fullerene dyads, the photoexcitation of a Zinc chlorin−C60 dyad results in an unusually long-lived radical ion pair which decays via first-order kinetics with a decay rate constant of 9.1 × 103 s-1. This value is 2−6 orders of magnitude smaller than values reported for all other Porphyrin or chlorin donor−acceptor of the molecule dyad systems. The formation of radical cations of the donor part and the radical anion of the acceptor part was also confirmed by ESR measurements under photoirradiation at low temperature. The photoexcitation of other dyads (free-base chlorin−C60, Zinc Porphyrin−C60, and free-base Porphyrin−C60 dyads) results in formation of the ion pairs which decay quickly to the triplet excited states of the chlorin or Porphyrin moiety via the higher lying radical i...

  • catalytic effects of dioxygen on intramolecular electron transfer in radical ion pairs of Zinc Porphyrin linked fullerenes
    Journal of the American Chemical Society, 2001
    Co-Authors: Shunichi Fukuzumi, Hiroshi Imahori, Hiroko Yamada, Mohamed E Elkhouly, Mamoru Fujitsuka, Osamu Ito, Dirk M Guldi
    Abstract:

    Dioxygen accelerates back electron transfer (BET) processes between a fullerene radical anion (C60) and a radical cation of Zinc Porphyrin (ZnP) in photolytically generated ZnP.+-C60.- and ZnP.+-H2P-C60.- radical ion pairs. The rate constant of BET increases linearly with increasing oxygen concentration without, however, forming reactive oxygen species, such as singlet oxygen or superoxide anion. When ferrocene (Fc) is used as a terminal electron donor moiety instead of ZnP (i.e., Fc-ZnP-C60), no catalytic effects of dioxygen were, however, observed for the BET in Fc+-ZnP-C60.-, that is, from C60.- to the ferricenium ion. In the case of ZnP-containing C60 systems, the partial coordination of O2 to ZnP.+ facilitates an intermolecular electron transfer (ET) from C60.- to O2. This rate-determining ET step is followed by a rapid intramolecular ET from O2.- to ZnP.+ in the corresponding O2.--ZnP.+ complex and hereby regenerating O2. In summary, O2 acts as a novel catalyst in accelerating the BET of the C60.--ZnP.+ radical ion pairs.

Helge Lemmetyinen - One of the best experts on this subject based on the ideXlab platform.

  • sequential photoinduced energy and electron transfer directed improved performance of the supramolecular solar cell of a Zinc Porphyrin Zinc phthalocyanine conjugate modified tio2 surface
    Journal of Physical Chemistry C, 2013
    Co-Authors: Kati Stranius, Navaneetha K Subbaiyan, Preston Dsouza, Helge Lemmetyinen, Nikolai V Tkachenko, Francis Dsouza
    Abstract:

    Improved performance of a photosynthetic antenna–reaction center mimicking supramolecular solar cell is demonstrated. Toward this, Porphyrin–phthalocyanine conjugates connected by amide linkers, as wide-band capturing solar energy harvesting materials, have been newly synthesized and characterized. Efficient singlet–singlet energy transfer from the Zinc or free-base Porphyrin to phthalocyanine is evidenced from steady-state emission and transient absorption studies in nonpolar and polar solvents. Further, the dyad was immobilized via axial coordination of Zinc Porphyrin of the dyad on semiconducting TiO2 surface modified with axial coordinating ligand functionality, phenylimidazole. Photoelectrochemical studies revealed improved performance of this cell compared to either Zinc Porphyrin or Zinc phthalocyanine only modified electrodes under similar experimental conditions. Transient absorption studies performed on the dyad immobilized on glass/TiO2 surface suggested that upon excitation of the axially coor...

  • ultrafast excitation transfer and charge stabilization in a newly assembled photosynthetic antenna reaction center mimic composed of boron dipyrrin Zinc Porphyrin and fullerene
    Faraday Discussions, 2011
    Co-Authors: Francis Dsouza, Mohamed E Elkhouly, Helge Lemmetyinen, Nikolai V Tkachenko, Melvin E Zandler, Channa A Wijesinghe, Jessica Hudson, Marja Niemi, Shunichi Fukuzumi
    Abstract:

    A self-assembled supramolecular triad as a model to mimic the light-induced events of the photosynthetic antenna-reaction center, that is, ultrafast excitation transfer followed by electron transfer ultimately generating a long-lived charge-separated state, has been accomplished. Boron dipyrrin (BDP), Zinc Porphyrin (ZnP) and fullerene (C60), respectively, constitute the energy donor, electron donor and electron acceptor segments of the antenna-reaction center imitation. Unlike in the previous models, the BDP entity was placed between the electron donor, ZnP and electron acceptor, C60 entities. For the construction, benzo-18-crown-6 functionalized BDP was synthesized and subsequently reacted with 3,4-dihydroxyphenyl functionalized ZnP through the central boron atom to form the crown-BDP-ZnP dyad. Next, an alkyl ammonium functionalized fullerene was used to self-assemble the crown ether entity of the dyad via ion–dipole interactions. The newly formed supramolecular triad was fully characterized by spectroscopic, computational and electrochemical methods. Steady-state fluorescence and excitation studies revealed the occurrence of energy transfer upon selective excitation of the BDP in the dyad. Further studies involving the pump–probe technique revealed excitation transfer from the 1BDP* to ZnP to occur in about 7 ps, much faster than that reported for other systems in this series of triads, as a consequence of shorter distance between the entities. Upon forming the supramolecular triad by self-assembling fullerene, the 1ZnP* produced by direct excitation or by energy transfer mechanism resulted in an initial electron transfer to the BDP entity. The charge recombination resulted in the population of the triplet excited state of C60, from where additional electron transfer occurred to produce C60•−:crown-BDP-ZnP•+ ion pair as the final charge-separated species. Nanosecond transient absorption studies revealed the lifetime of the charge-separated state to be ∼100 μs, the longest ever reported for this type of antenna-reaction center mimics, indicating better charge stabilization as a result of the different disposition of the entities of the supramolecular triad.

  • photosynthetic antenna reaction center mimicry sequential energy and electron transfer in a self assembled supramolecular triad composed of boron dipyrrin Zinc Porphyrin and fullerene
    Journal of Physical Chemistry A, 2009
    Co-Authors: Eranda Maligaspe, Navaneetha K Subbaiyan, Helge Lemmetyinen, Nikolai V Tkachenko, Melvin E Zandler, Raghu Chitta, Francis Dsouza
    Abstract:

    A self-assembled supramolecular triad, a model to mimic the photochemical events of photosynthetic antenna−reaction center, viz., sequential energy and electron transfer, has been newly constructed and studied. Boron dipyrrin, Zinc Porphyrin, and fullerene respectively constitute the energy donor, electron donor, and electron acceptor segments of the antenna−reaction center mimicry. For the construction, first, boron dipyrrin was covalently attached to a Zinc Porphyrin entity bearing a benzo-18-crown-6 host segment at the opposite end of the Porphyrin ring. Next, an alkyl ammonium functionalized fullerene was used to self-assemble the crown ether entity via ion−dipole interactions. The newly formed supramolecular triad was fully characterized by spectroscopic, computational, and electrochemical methods. Selective excitation of the boron dipyrrin moiety in the dyad resulted in energy transfer over 97% efficiency creating singlet excited Zinc Porphyrin. The rate of energy transfer from the decay measurement...

Nikolai V Tkachenko - One of the best experts on this subject based on the ideXlab platform.

  • sequential photoinduced energy and electron transfer directed improved performance of the supramolecular solar cell of a Zinc Porphyrin Zinc phthalocyanine conjugate modified tio2 surface
    Journal of Physical Chemistry C, 2013
    Co-Authors: Kati Stranius, Navaneetha K Subbaiyan, Preston Dsouza, Helge Lemmetyinen, Nikolai V Tkachenko, Francis Dsouza
    Abstract:

    Improved performance of a photosynthetic antenna–reaction center mimicking supramolecular solar cell is demonstrated. Toward this, Porphyrin–phthalocyanine conjugates connected by amide linkers, as wide-band capturing solar energy harvesting materials, have been newly synthesized and characterized. Efficient singlet–singlet energy transfer from the Zinc or free-base Porphyrin to phthalocyanine is evidenced from steady-state emission and transient absorption studies in nonpolar and polar solvents. Further, the dyad was immobilized via axial coordination of Zinc Porphyrin of the dyad on semiconducting TiO2 surface modified with axial coordinating ligand functionality, phenylimidazole. Photoelectrochemical studies revealed improved performance of this cell compared to either Zinc Porphyrin or Zinc phthalocyanine only modified electrodes under similar experimental conditions. Transient absorption studies performed on the dyad immobilized on glass/TiO2 surface suggested that upon excitation of the axially coor...

  • ultrafast excitation transfer and charge stabilization in a newly assembled photosynthetic antenna reaction center mimic composed of boron dipyrrin Zinc Porphyrin and fullerene
    Faraday Discussions, 2011
    Co-Authors: Francis Dsouza, Mohamed E Elkhouly, Helge Lemmetyinen, Nikolai V Tkachenko, Melvin E Zandler, Channa A Wijesinghe, Jessica Hudson, Marja Niemi, Shunichi Fukuzumi
    Abstract:

    A self-assembled supramolecular triad as a model to mimic the light-induced events of the photosynthetic antenna-reaction center, that is, ultrafast excitation transfer followed by electron transfer ultimately generating a long-lived charge-separated state, has been accomplished. Boron dipyrrin (BDP), Zinc Porphyrin (ZnP) and fullerene (C60), respectively, constitute the energy donor, electron donor and electron acceptor segments of the antenna-reaction center imitation. Unlike in the previous models, the BDP entity was placed between the electron donor, ZnP and electron acceptor, C60 entities. For the construction, benzo-18-crown-6 functionalized BDP was synthesized and subsequently reacted with 3,4-dihydroxyphenyl functionalized ZnP through the central boron atom to form the crown-BDP-ZnP dyad. Next, an alkyl ammonium functionalized fullerene was used to self-assemble the crown ether entity of the dyad via ion–dipole interactions. The newly formed supramolecular triad was fully characterized by spectroscopic, computational and electrochemical methods. Steady-state fluorescence and excitation studies revealed the occurrence of energy transfer upon selective excitation of the BDP in the dyad. Further studies involving the pump–probe technique revealed excitation transfer from the 1BDP* to ZnP to occur in about 7 ps, much faster than that reported for other systems in this series of triads, as a consequence of shorter distance between the entities. Upon forming the supramolecular triad by self-assembling fullerene, the 1ZnP* produced by direct excitation or by energy transfer mechanism resulted in an initial electron transfer to the BDP entity. The charge recombination resulted in the population of the triplet excited state of C60, from where additional electron transfer occurred to produce C60•−:crown-BDP-ZnP•+ ion pair as the final charge-separated species. Nanosecond transient absorption studies revealed the lifetime of the charge-separated state to be ∼100 μs, the longest ever reported for this type of antenna-reaction center mimics, indicating better charge stabilization as a result of the different disposition of the entities of the supramolecular triad.

  • photosynthetic antenna reaction center mimicry sequential energy and electron transfer in a self assembled supramolecular triad composed of boron dipyrrin Zinc Porphyrin and fullerene
    Journal of Physical Chemistry A, 2009
    Co-Authors: Eranda Maligaspe, Navaneetha K Subbaiyan, Helge Lemmetyinen, Nikolai V Tkachenko, Melvin E Zandler, Raghu Chitta, Francis Dsouza
    Abstract:

    A self-assembled supramolecular triad, a model to mimic the photochemical events of photosynthetic antenna−reaction center, viz., sequential energy and electron transfer, has been newly constructed and studied. Boron dipyrrin, Zinc Porphyrin, and fullerene respectively constitute the energy donor, electron donor, and electron acceptor segments of the antenna−reaction center mimicry. For the construction, first, boron dipyrrin was covalently attached to a Zinc Porphyrin entity bearing a benzo-18-crown-6 host segment at the opposite end of the Porphyrin ring. Next, an alkyl ammonium functionalized fullerene was used to self-assemble the crown ether entity via ion−dipole interactions. The newly formed supramolecular triad was fully characterized by spectroscopic, computational, and electrochemical methods. Selective excitation of the boron dipyrrin moiety in the dyad resulted in energy transfer over 97% efficiency creating singlet excited Zinc Porphyrin. The rate of energy transfer from the decay measurement...

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